The present invention relates generally to an improved method for producing a semiconductor laser device.
Opto-electronic integrated circuits (OEIC) consist of optical devices such as optical switches, branching filters/collectors, light detectors/emitters, etc., integrated on the same substrate with electronic circuits such as amplifying circuits for photodetectors, driving circuits for light emitters and discriminator decision circuits. Research in integrating electronic circuits and optical elements by epitaxially growing luminescent material such as GaAs on a silicon substrate is actively pursued.
The nucleus of an OEIC semiconductor laser device's light emitter is its resonator. Difficulties with the conventional method of fabricating OEIC's arise from the fact that the mirror surfaces of the resonator are cleavage surfaces of crystal. Since the cleavage surfaces undesirably penetrate the underlying substrate, the length of the OEIC resonator is limited with respect to the integration of electronic components.
A further technique in the prior art is chemical and dry etching commonly used to form the mirror surfaces of resonators. These methods are inherently undesirable, however, since they may damage the mirror surfaces and are not as accurate as cleavage methods, which are capable of creating mirror surfaces with dimensions on the order of submicrons.
A two-dimensional array of a semiconductor laser device can be formed on an OEIC by guiding laser beams in a specified direction, including right angles, off the surface of an epitaxial film. Since the cleavage surfaces in conventional devices penetrate the substrate, however, arrays cannot be constructed.
A method for emitting a laser beam perpendicular to the epitaxial surface via a 45 degree mirror monolithically formed through etching is known in the art. To form the required resonator, however, a complicated two step process is required. First, both ends of the resonator are formed using mirror-surface etching at right angles to the substrate. Second, the mirror planes are formed through anisotropic etching at a 45.degree. angle to the substrate. Taking the spatial arrangement and attenuation of a laser beam into consideration, the distance between the resonator surface and the mirror planes must be minimized. The two step etching process of the prior art, however, forms a relatively large gap between the end of the resonator and the mirror plane.